The present invention relates generally to strings of lights such as those used for decorating Christmas trees.
Strings of lights, that is, plural lights wired together to be powered from a plug inserted into a wall outlet, are used to decorate Christmas trees and homes. They are used for both interior decorating and exterior decorating.
For a 100-lamp light set, there are typically two types: two series circuits and three series circuits. The light sets both work the same, but the difference between the two is the brightness. One type is normal brightness and the other type is referred to as xe2x80x9csuperxe2x80x9d bright. The difference in lamp brightness is attributable to the lamp voltage. The two series circuits have a lower lamp voltage per lamp (2.5V) i.e. 125/50. Each series circuit has 50 lamps.
The three circuit set has a higher per-lamp voltage of (3.5V) i.e. 125/35, for a much higher voltage and brighter lamp. Each circuit has 35 lamps in it. This means that a xe2x80x9csuper brightxe2x80x9d 100-light set actually has 105 lamps in it.
Prior art light strings have the following parts: (1) an AC plug containing two 3 Amp fuses with 1 line side and 1 neutral side, (2) 6xe2x80x3-7xe2x80x3 interconnecting wires (22AWG) between each socket in the series; (3) 1 AC receptacle at the end of the set; (4) 1 xe2x80x9creturnxe2x80x9d or neutral line (22AWG) from the receptacle on the end of the set and then back to the last socket of each circuit in the set until it eventually terminates at the plug; (5) 1 xe2x80x9chotxe2x80x9d line (22AWG) from the plug to the first socket in the first circuit in the set; (6) 1 xe2x80x9chotxe2x80x9d line (22AWG) from the plug to the additional series circuits remaining in the set; (7) plastic light sockets for two wires; (8) plastic light sockets for three wires; (9) two brass electrical terminals per wire; (10) plastic lamp plugs to hold the lamps; and (11) miniature glass lamps.
Using the xe2x80x98Super Brightxe2x80x99 set as an example, the prior art light string has 104, 6xe2x80x3 or 7xe2x80x3 wires, depending on overall set length, each wire is cut, both ends of each striped back xc2xcxe2x80x3, and bundled in groups of 104. The two, brass electrical terminals, are manually crimped onto each wire; one at each end, for a total of 208 terminalsxe2x80x94and 208 hand operations. Some of these terminals will have two wires crimped into them to cascade a line, such as the xe2x80x9creturnxe2x80x9d line or the xe2x80x9cAC linexe2x80x9d, from one circuit to the next. The xe2x80x9creturnxe2x80x9d line (as an example) is about 18 ft. in length and runs from the AC plug to the last socket of the first circuit, whereas the xe2x80x9cAC linexe2x80x9d runs from the AC plug (male) to the first socket in the first group. A second 18 ft. xe2x80x9creturnxe2x80x9d wire is also crimped into the same terminal to pass the xe2x80x9creturnxe2x80x9d to the last socket of the second circuit. Finally, a third, 18 ft. xe2x80x9creturnxe2x80x9d line is crimped to the xe2x80x9creturnxe2x80x9d line of the second set to pass the xe2x80x9creturnxe2x80x9d line to the last socket in the third and final set. From that last socket another, shorter xe2x80x9creturnxe2x80x9d line (6xe2x80x3) is crimped into the last socket xe2x80x9creturnxe2x80x9d line which terminates at the AC receptacle (female) at the end of the set.
Every lamp socket is connected in the series via a 6xe2x80x3 line having a terminal crimped onto each end, with the last socket in each series circuit having two wires crimped in one of the terminals to cascade the line to the next series circuit. So the final tally on individual wires in a series light set is 109 wires; all with crimped on terminals at each end.
During assembly, each terminal and wire is inserted by hand through the bottom of the socket and then pulled down into a crevice (mounting) to hold the terminal firmly in place inside the socket. This insertion, mounting and pulling operation happens two times to each socket; once, for each terminal. When there are three or four wires, the operation takes considerably longer, as the double wire terminals do not easily fit or bend for mounting into the crevice. Even when a larger, special socket is used, the insertion of the second terminal is still very difficult, often causing wires to be cut or to be pulled out of a terminal and eventually causing a short circuit.
Furthermore, the bottoms of the sockets are open, so water from rain, snow or spills can enter the socket, and in colder regions where there is ice in winter, often salt-saturated water penetrates the sockets causing corrosion and arcing. The wires are crimped into brass terminals which during the assembly process are twisted and pulled, often loosening wires from the crimp and causing the crimp connection to loosen and the wires can pull out easily or worse, cause arcing inside the socket producing sparksxe2x80x94one of the primary causes of Christmas tree fires and light set failures.
Furthermore, the open bottom allows atmospheric conditions to accelerate contact breakdown due to acidic corrosion, Galvanic effects due to dissimilar metals, electrical current flow and the presence of salt-laden moisture. This greatly reduces the life and safety of the prior art light sets.
Finally, most of the miniature light set manufacturers today cannot pass the current UL588 test for xe2x80x98Leakage currentxe2x80x99 due to the open bottom of the socket, consequently they have to put a tag on the light set that says xe2x80x9cFor indoor use onlyxe2x80x9d; however, many people disregard this notice and use the light sets outside, a dangerous and hazardous situation.
Thus there is a need for a safer and easier to manufacture light set.
The present invention is a string of lights comprising plural groups of lights, each light in each group being electrically in parallel with each other light in the same group, each group of lights being electrically in series with each other group in the set and the string being terminated in a plug that rectifies incoming alternating current to direct current and limits current through the circuit. Importantly, in each group of lights, and also electrically in parallel with each other light in the group, is a device that controls the lights in that group. This device can control the group in several ways. In at least one way, it allows the current to flow across that group from the previous group to the next one without shorting the whole light string in the event that one or more of the lights in that group is removed or burns out. In another embodiment, it can turn out the lights in that group in a programmed sequence or on command.
The present invention is also a light socket for use in a string of lights that allows manufacture of the present string, or indeed, of any string of lights where the present socket is used, to be done much more easily. In fact, it allows the automation of the light string manufacturing process.
The light socket includes a sleeve, a base, and a pair of piercing terminals. There are three variations on the light socket depending on whether it is a xe2x80x9cfour wirexe2x80x9d configuration, a xe2x80x9cthree wirexe2x80x9d configuration or a xe2x80x9cthree wirexe2x80x9d with a device. A xe2x80x9ctwo-wirexe2x80x9d configuration is also possible.
A feature of the present invention is that it operates at a lower electrical current than prior light strings. A lower current requirement in turn translates into a cooler light string and a safer light string.
Another feature of the present invention is that the use of device in each group of lights makes it easier to determine which bulb is missing or burned out because the remaining lights will continue to light.
Still another feature of the present invention is that because of its simple design, the present light string can be assembled much more quickly by hand and can be fabricated by machine.
Yet another feature of the present invention is the incorporation of a programmable device into each group or indeed in each socket. This feature enables control of the lights in ways previously unknown.
These and other features and their advantages will become apparent to those skilled in the art of the manufacturing and use of strings of lights from a careful reading of the Detailed Description of Preferred Embodiments, accompanied by the drawings.